Alert archive / Iowa / Dense Fog Advisories in 2021

Dense Fog Advisory 5, NWS Quad Cities, IA

February 3, 202121 counties in Iowa; 11 counties in Illinois; Clark County, Scotland County, Missouri

NWS Quad Cities, IA issued this dense fog advisory at Feb 3, 2021, 1:04 AM CST for 21 counties in Iowa; 11 counties in Illinois; Clark County, Scotland County, Missouri. It was in force for 10 hr.

The area

The counties it named.

The facts

Issued
Feb 3, 2021, 1:04 AM CST (07:04 UTC)
Expired
Feb 3, 2021, 11:00 AM CST
In force
10 hr
Issued by
NWS Quad Cities, IA
All 34 counties

Benton County, IA, Buchanan County, IA, Cedar County, IA, Clinton County, IA, Delaware County, IA, Des Moines County, IA, Dubuque County, IA, Henry County, IA, Iowa County, IA, Jackson County, IA, Jefferson County, IA, Johnson County, IA, Jones County, IA, Keokuk County, IA, Lee County, IA, Linn County, IA, Louisa County, IA, Muscatine County, IA, Scott County, IA, Van Buren County, IA, Washington County, IA, Bureau County, IL, Carroll County, IL, Hancock County, IL, Henderson County, IL, Henry County, IL, Jo Daviess County, IL, Mercer County, IL, Putnam County, IL, Rock Island County, IL, Stephenson County, IL, Whiteside County, IL, Clark County, MO, Scotland County, MO

The radar

The Quad Cities radar (KDVN), 41 km from the middle of the area, began a volume at 07:10 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Davenport, (KDVN), launched 00:00Z, 7.1 hours before the alert went out and 47 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Davenport, at 00:00Z on 2021-02-03Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 0 joules per kilogram.LCL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Davenport, at 00:00Z on 2021-02-03The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 32 square meters per square second.1939587897117Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
0 J/kg
Mixed-layer CIN
No buoyant parcel
Mixed-layer LCL
1014 m above ground
0-6 km bulk shear
53 kt
0-1 km storm-relative helicity
32 m²/s²
0-3 km storm-relative helicity
65 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this dense fog advisory went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Quad Cities, IA wrote its last area forecast discussion before this dense fog advisory went out at Feb 2, 10:21 PM CST, 2 hours 43 minutes earlier.

Area forecast discussion, Feb 2, 10:21 PM CST, 2 hours 43 minutes before
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Hazardous weather outlook, Feb 2, 3:52 PM CST, 9 hours 12 minutes before
Hazardous Weather Outlook
National Weather Service Quad Cities IA IL
352 PM CST Tue Feb 2 2021

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-032200-
Buchanan-Delaware-Dubuque-Benton-Linn-Jones-Jackson-Iowa-Johnson-
Cedar-Clinton-Muscatine-Scott-Keokuk-Washington-Louisa-Jefferson-
Henry IA-Des Moines-Van Buren-Lee-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-Mercer-Henderson-
Warren-Hancock-McDonough-Scotland-Clark-
352 PM CST Tue Feb 2 2021

This Hazardous Weather Outlook is for portions of north central
Illinois...northwest Illinois...west central Illinois...east
central Iowa...northeast Iowa...southeast Iowa and northeast
Missouri.

.DAY ONE...THIS AFTERNOON AND TONIGHT

Areas of fog, some dense, can be expected tonight reducing
visibilities to less than a mile. There may also be patchy slick
spots on roadways.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

Thursday, freezing rain and rain will spread across the entire
area in the morning hours, with slick roads likely. By afternoon,
a powerful cold front will quickly change the rains to snow, with
accumulating snow likely through the evening hours. At this time,
several inches of snow is possible, mainly along and north of
Interstate 80. Blowing snow and rapidly falling temperatures in
the late afternoon and evening will also be accompanied by a flash
freeze of wet roads. Blowing snow will continue to be a threat
through Thursday night, as temperatures fall to the single digits
above zero to the lower teens. Wind chills by Friday morning may
reach as low as -20.

Bitterly cold weather is forecast through Monday. Wind chills of
-20 to -30 are likely each night, with daytime highs only in the
 single digits above zero.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed through tonight.

Haase

In the hours before

Special weather statement, Feb 2, 9:09 PM CST, 3 hours 55 minutes before
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Special weather statement, Feb 2, 10:31 PM CST, 2 hours 33 minutes before
Special Weather Statement
National Weather Service Quad Cities IA IL
1031 PM CST Tue Feb 2 2021

IAZ042-053-054-066-068-ILZ001-002-007-009-015>018-030645-
Dubuque-Jones-Jackson-Clinton-Scott-Jo Daviess-Stephenson-Carroll-
Whiteside-Rock Island-Henry IL-Bureau-Putnam-
Including the cities of Dubuque, Anamosa, Maquoketa, Clinton,
Davenport, Bettendorf, Galena, Freeport, Mount Carroll, Sterling,
Moline, Rock Island, Geneseo, Princeton, and Hennepin
1031 PM CST Tue Feb 2 2021

...Patchy Dense Fog...

Clearing skies and light winds will continue to allow areas of
fog to develop into the overnight. The fog will be dense in
spots, especially in river valleys and other low lying areas.
The patchy nature of the fog is likely to result in rapid
fluctuations in visibility over short distances. If traveling be
prepared for sudden changes in visibility. When encountering dense
fog please use low beam headlights, slow down, and give yourself
plenty of braking distance. A dense fog advisory may be needed if
the dense fog becomes widespread.

The office that day

Everything else NWS Quad Cities, IA issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Feb 3, 4:01 AM CSTWinter Storm WatchDVNBenton, Buchanan, Cedar, Clinton, Delaware, Dubuque and 7 more11 hr
Feb 3, 4:01 AM CSTWinter Weather AdvisoryDVNBenton, Buchanan, Cedar, Clinton, Delaware, Des Moines and 15 more56 hr
Feb 3, 2:56 PM CSTWinter Storm WarningDVNBenton, Buchanan, Cedar, Clinton, Delaware, Des Moines and 13 more36 hr

Nearby

Dense Fog Advisories in Iowa, 2021Dense Fog Advisories in Illinois, 2021Dense Fog Advisories in Missouri, 2021Every dense fog advisory in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.